Category: SOLAR ENERGY 3

Stagnation temperature

Equation (8.41) shows that the temperature will continue to increase with time, which can be a problem, especially when the water does not flow to put some heat load on the collector. At this condition, when water is not flowing, the device will increase in temperature and reach a steady-state temperature called the stagnation temperature. […]

Recirculation of water

The temperature rise of water from a flat plate solar energy collector is small and of order 20 °C which is not hot enough for residential hot water which is delivered at approximately 50°C. This shortcoming is overcome by recirculating the water within a tank, as shown in Fig. 8.15. The useful heat is constantly […]

The effect of a cover

Many flat plate solar absorbers have a cover to reduce heat loss via the greenhouse effect; a schematic is shown in Fig. 8.7. This complicates the analysis for two reasons. Firstly, the amount of radiation that reaches and is absorbed by the absorber plate must be determined. This is written || ат || Pd (в), […]

The basic system

The basic system is shown in Fig. 8.1, which consists of a glass cover over an absorber plate which is in thermal contact with the flowing water that enters and exits the device. Insulation at the back of the device, as well as around the edges (not shown), reduces thermal losses. The glass cover is […]

The solar tower

The passive solar cooling effect promoted by the solar chimney is a pow­erful element of building design especially in warm climates. However, the flow of air is not harnessed to generate useful work. Remarkably, Leonardo da Vinci (1452-1519) envisioned a spit that was turned by the rising air in a fireplace as shown in Fig. […]

The solar chimney

Now that we know how a chimney works we can use the above analysis to determine a way to cool a house with a chimney! This is similar to the cooling effect mentioned in the above example where cooler, out­side air is directly brought into the house. Air circulation is promoted through the house or […]